Piston



"Feb. 17, 1931. A. NELSON 1,792,504

' PISTON Original Filed March 1a, 1927 4 Sheets-Sheet 1 Feb. 17, 1931.

A. L. NELSON PISTON Original Filed March 16, 1927 4 Sheets-Sheet 2 A. L. NELSON Feb. 17, 1931.

PISTON 4 Sheets-Sheet 3 Original Filed March 16, 1927 Feb. 17, 1931.

IIIIIHVIIIVIIIHIIM A. L. NELSON PISTON Original Filed March 16, 1927 4 Sheets-Sheet 4 PatentedFeb. 11, 1931.

UNITED STATES PATENT OFFICE ADOLPH L. NELSON, OF DETROIT, MICHIGAN, ASSIGNOR 1 0 BOHN ALUMINUM & BRASS CORPORATION, OF DETROIT, MICHIGAN risron Application filed March 16, 1927, Serial K0. 175,645. Renewed July 3, 1930.

This invention relates to pistons, particularly to pistons for use in internal combustionengines, and aims to improve the construction and operative results of such pistons.

I have previously disclosed in my Patent N 0. 1,454,761 granted May 8, 1923, the use of relatively inexpansible struts to overcome the diflioulties due to the'high rate of thermal expansion of certain light-weight piston materials, such as aluminum alloys. The-present invention aims to utilize the principles heretofore disclosed and to produce an improved piston by the cooperation of certain novel features of construction hereinafter more fully set forth. i

In the drawings: Fig. 1 is an elevation partly in section of a piston embodying the invention;

Fig. 2 is a section on line 22 of Fig. 1; Fig. 3 is a section on line 3-3 of Fig. 2; Fig. 4 is a longitudinal section through a piston embodying certain modifications;

Fig. 5 is a longitudinal section taken at Fig. 6 is an elevation of a strut;

Fig. 7 is a top plan of a strut;

Fig. 8 is a section on line 88 of Fig. 2;

Fig. 9 is a section similar to Fig. 3 but showing a modified construction;

Fig.-l0 is a longitudinal section through a further modification;

Fig. 11 is a longitudinal section taken at right angles to Fig. 10;

Fig. 12 is a view looking upward from the bottom of a piston as shown in Figs. 10 and 11 drawings more specifically, the piston, which is preferably formed of light-weight material, such as an alloy of aluminum, comprises a head portion and a skirt portion, the latter term applying to the zone lying below the head.

The piers 10, which depend from the head, are reinforced internally by ribs 11 and externally by a rib 12, and have the piston pin bosses 13 formed therein. Below the pin bosses the piers connect with the horizontal arcuate webs 14, shown more clearly in Fig. 8, which are joined to the lower circular part 15 of the skirt. On opposite sides of the skirt Referring to the cylindrical bearing portions 16 and 17 extend Y upwardly from the circular part 15 of the skirt. These bearing portions are discontinuous from the head and from the upper part of the piers and have homogeneous connections with the and webs 14.

The circular portion 15 is reinforced at points directly below the openings 20 which lie between the piers and the bearing portions. This reinforcing may be accomplished in any convenient manner as by thickening the skirt at these points to form the pads 21.

iston ring grooves 18 are cut into the side of the piston head, the lowest groove being positioned so that the slots 19, between the bearing portions 16 and 17 and the head, are located at the bottom of this groove.

The skirt is provided with a slot or slots extending upwardly from the lower end thereof. ,A single slot may be placed in one of the semi-cylindrical bearing portions as at 22 in Figs. 1 and 2, or a slot may be formed upwardly below each piston pinboss and terminating just below the boss, as shown at 23 in Figs. 4 and 5.

In cases where the slotting shown in Figs. 4 and 5 does not make the'lower end of the skirt sufliciently resilient, the slots'ma be continued up through the lower wall 0 the piston pin bearing as shown in Figs. 10--12.

11 this species a column 32 extends downwardly from the inner end of each pin bearing. A vertical hole 33 runs through the column, and the slot 34 extends upwardly into the axial opening of the pin bearing and communicates with hole 33.

A pair of flat plate-like struts 24 extend across the skirt and connect oppositeedges of the bearing portions. 16 and 17. These struts may be formed of any relatively inexpansible material, i. e., any material having a lower coefiicient of thermal'expansion than the material of the skirt, and are of the general shape shown in Figs. 6 and 7. A notch 25 is formed in each end of the strut, leaving piers through the ring 15 strut, as clearly shown in Figs. 3 and 7 Holes 28 are formed through the strut, and a semi-circular notch 29 is cut into one side of the strut. Along the upper line of the strut the ends are dropped below the level of the central part of the strut, as will be clear from Figs. 5 and 6.

In mo ding the piston the struts are first placed in the mold and are accurately positioned by reason of projections carried by the mold fittingl snugly into the holes 28. In this manner t e struts are positively held against movement in any direction during the molding process. Since the head of the piston is formed in the bottom of the mold, the strut is held in the mold with the narrow projections 27 uppermost. As the metal is poured it cools rapidly, so that while the relatively hot metal will flow readily around the wide pro ection 26, it has cooled somewhat by the time it reaches projection 27, and would not flow around this projection as readily as it did around projection 26 if projection 27 were as wide as projection 26. By forming projection 27 relatively narrow the flow of metal therearound is facilitated.

By bending the ends of the struts it is possible to obtain a longer joint between the strut and the skirt without adding any metal to the skirt, thereby obtaining a better bond without additional weight. Due to the fact that the ends of the struts are dropped below the level of the top of the central portion, it is possible to insert a cutter into the aperture 20 above the strut in order to cut a slot 35 connecting the opening 20 with an end of slot 19. The shape of the strut makes it possible to perform this operation without sacrificing the width of the strut, and therefore its strength, in the center.

The piston may be formed with the intermediate part of the struts embedded in the material of the piers as shown in Figs. 4 and 5. In this case the holes 20 may be formed in the struts to permit the metal to flow therethrough to strengthen and solidify the structure. But preferably the intermediate part of the strut lies alongside of the pier but is free, i. e., not surrounded by the material of the pier, this structure being illustrated in Figs. 1-3. In this latter construction there will be less heat transmitted through the struts to the upper ends of the bearing portions.

This piston is manufactured by casting the piers in contact with the struts, and'while there is a tendency for the piers to shrink slightly away from the struts on cooling, they are substantlally in contact with the piers at all times.

In a piston constructed in the 'manner thus far set forth, the ends of the struts are embedded in the bearin portions, and hence the relativel inexpansib e struts restrain the tendency o the bearing portions to expand outbearing portions,

wardly as the piston becomes heated in use. The semi-cylindrical bearing portions are di rectly joined at their lower ends to the piers by connections strong enough to carry all the operating loads on the bearing portions. This construction relieves the joints between the strut and the skirt of all complex operating stresses, and reduces the loading on the strut joints to that of a simple spacing load in one direction only. Another advantage of the structure is that it permits leaving the strut free at its center as shown in Figs. 1-3.

The difliculties due to the high rate of expansion of light-weight piston materials may be overcome in several distinct ways. The tendency of the piston to expand too rapidly may be positively restrained, or the piston may be positively held in an expanded condition to revent slapping when the motor is cold. 11 the species thus fardisclosed the struts operate as a positive restraint upon the expansion of the piston. In the species illustrated in Fig. 9 the struts act as spacers to prevent slapping when the motor is cold.

In this species the ends of the strut are formed with rounded dome-like ends 31. In casting) the piston, these ends form sockets in the caring portions, but are not embedded therein and hence have no positive connection therewith. The intermediate part of. the strut may be embedded in the pier or may be left free as shown in Fig. 9. In this construction there is a minimum of heat transmitted through the strut to the upper part of the since the strut is not embedded in either pier or bearing portions.

When the piston of Fig. 9 cools after casting the skirt tends to contract, but the struts 24 act as spacers to positively hold the bearing portions in the positions designed to give a certain piston clearance when the piston is cold, thereby setting up certain stresses in the bearing portions 16 and 17. As the piston warms up in operation stresses are never entirely relieved on account of the fact that the operating temperatures are always lower than the casting temperatures. As a result the bearing portions never expand away from the ends of the struts.

I claim 1. A piston comprising a head, piers deending from the head, piston pin bosses ormed in the piers, bearin portions formed of light-weight material, a omogeneous connectlon between each bearing portion and each pier, and a pair of fiat, plate-like struts of material less expansible than the material of the bearing portions, the struts extending between the bearing portions, the intermediate portions of the struts being free from the piers.

2. A piston comprising a head, piers depending from the head, piston pin bosses formed in the piers, a lower circular portion attached to the piers, semi-cylindrical bearing. portions homogeneous with the circular portion andhaving their upper ends discontinuous from the head and piers, the bearing portions being formed of light-weight material, and a pair of flat, plate-like chordal struts of material less expansible than the material of the bearing portions, said struts extending between the bearing portions, the intermediate portions of the struts being free from the piers.

3. A piston as set forth in claim 2 in which the struts are substantially in contact with the piers.

4. A piston as set forth in claim 2 in which the struts are substantially in contact with the piers above the pin bosses.

5. A piston comprising a head, bearing portions formed of light-weight material,

.and a pair of struts of material less expansible than the material of the bearing portions, the ends of each strut being bent at an angle to the main body of the strut, the bent portions being embedded in the bearing portions.

6.. A piston comprising a head, bearing portions formed of light-weight material, and a pair of struts of material less expansible than the material of the bearing portions, the ends of each strut being embedded in the bearing portions, part of each embedded end being bent substantially parallel to the outer wall of the bearing portion.

7 A piston comprising bearing portions formed of light-weight material, struts connecting the bearing portions, each strut being in the form of a flat, plate-like member, there being a semi-circular notch cut in one longitudinal edge of the strut.

8. A piston comprising bearing portions formed of light-weight material, struts connecting the bearing portions, each strut being in the form of a flat, plate-like member,- each end of the strut being notched to form two projections, one projection being wider than the other. I

9. As an article of manufacture, a piston strut in the form of a fiat, plate-like member, projections of unequal width extending from each end of the strut.

10. As an article of manufacture, as piston strut in the form of a flat, plate-like member, there being a semi-circular notch cut in one longitudinal edge of the strut.

11. As an article of manufacture, a piston strut in the form of a flat, plate-like member, projections'of unequal width extending from each end of the strut, a semi-circular notch cut in one longitudinal edge of the strut, and positioning means formed on the strut.

12. A piston comprising a head, piers depending from the head, piston pin bosses formed in the piers, bearing portions formed of light-weight material, a homogeneous connection between each bearing portion and each pier, and a pair of struts of material less expansible than the materialof the hearing portions, the struts having their ends embedded in the material of the bearing portions, the intermediate portions of the struts being free from the piers but substantially material less expansible than the material of the bearing portions, the struts having "their ends embedded in the material of the bearing portions, the intermediate portions of the struts being free from the piers but substantially in contact with the piers, there being a connection between the bearing portions and the piers in addition to the struts, said connection being designed to carry the bearing portions.

14. A piston comprising a head, piers depending from the head, arcuate webs connected to the lower ends of the piers, a circular portion attached to the webs, semi-cylindrical bearing portions extending upwardly from the circular portion, the sides of the bearing portions being discontinuous from the piers, the circular portion having an additional reinforcement below the aperture between the bearing portions and the piers.

15. A piston comprising a head, piers depending from the head, arcuate webs connected to the lower ends of the piers, a circular portion attached to the webs, semicylindrical bearing ortions extending upward- 1y from the circu ar portion, the sides of the bearing portions being discontinuous from the piers, the circular portion being thickened to form reinforcements below the arcuate webs and in line with the apertures between the bearing portions and the piers.

16. A iston comprising a head, bearing portions ormed of light-weight material, and a pair of struts of material less expansible than the material of the bearing portions, the upper edge of the ends of the struts being lower than the upper edge of the intermediate portion of the struts.

17. A piston comprising a head, bearing portions formed of light-weight material, and a pair of struts of material less expansible than the material of the bearing portions, each end of the strut carrying one or more bent fingers, the bent fingers being embedded in the bearing portions.

18. A piston comprising a head, piers depending from the head, a circular portion attached to the lower ends of the piers, semicylindrical bearing portions extending upwardly from the circular portion,the piston being formed. with. apertures between the piers and the bearing portions, the circular portion being thickened at four places to form reinforcing ads, each of the pads being located direct y below one of the apertures that lie between the bearing portions and the piers.

19. A piston comprising a head, piers depending fromthe head a circular portion attached to the lower ends of the piers, semicylindrical bearin portions extending upwardly from the clrcular portion, the circular portion being thickened at four places to form four segment-shaped reinforcing pads.

20. A piston comprising a head, piers depending from the head, a; circular portion attached to the lower ends of the piers, semicylindrical bearin portions extending upwardly from the circular portion, the piston being formed with apertures between the piers and the bearing portions, the circular portion being thickened at four places to form four segment-shaped reinforcing pads, each of the pads being located directly below oneof the apertures that lie between the bearing portions and the iers.

21. A iston comprising a ead piers depending iiom the head, a segment shaped web connected to the lower end of each'pier, a circular portion attached to the segmentshaped webs, semi-cylindrical bearing portions extending upwardly from the circular portion, the piston being formed with apertures between the piers and the bearing portions, the circular portion being thickened at four places to form four segment shaped reinforcing pads, each of the pads being located directly below one of the apertures that lie between the bearing portions and the piers.

22. A piston comprising a head, piers depending from the head, a segment-shaped web connected to the lower end of each per, a circular ortion attached to the segmentshaped we s, semi-cylindrical bearing portions extending upwardly from the circular portion, the head, piers and bearing portions eing formed 0 light-weight material, struts of material less expansible than the material of the head and extending between the bearing portions, the piston being formed with apertures between the piers and the bearing portions, the circular portion being thickened at four places to form four segment-shaped reinforcing pads, each of the pads beinglocated directly below one of the apertures that lie between the bearing portions and the piers. p 23. A piston comprising a head, bearing portions formed of light wei ht material, and

- a pair of struts of materia less expansible than the material of the bearing portions, the ends of each strut carrying a plurality of bent fingers, the bent fingers being embedded in the bearing portions.

In testimony whereof I aifix my si ature. ADOLPH L. NEL ON. 

